Mercury-tube switch



Dec. 29,1925. I 1,567,140

` w. G. HARTWIG MERCURY TUBE SWITCH Filed May 1`1, 1923 dit titl

dit

Patented Dec. 29, 1925.

UNITED STATES WILLIAM G. HARTWIG, 0F CHICAGO,A IQLLN'OIS.V

MERCURY-TUBE SWITCH.

Application led May 11, 1923. Serial No. 638,165.

To all whom z' may concern:

Be it known that I, VILLIAM G. HARTWIG, citizen of the United States, residing at Chicago, in the county of Cook and State l ot Illinois, have invented certain new and useful Improvements in Mercury-Tube Switches, of which the following is a specification.

Thisl invention relates to mercury tube switches adapted for use in closing electric circuits in response to changes in temperature in the room in which the switch is located and the present invention is a modification of that described and claimed in my application, Serial No. 614,741 tiled January 25, i923.

The principal object of the invention is to provide improved means for automatically closing the circuit in case the mercury 4tube is broken. A further object is to provide an improved arrangement of the metallic spring contacts adapted to be connected automatically upon the breaking or displacement of the mercury tube. A further object is to provide an enclosed casing for the mercury tube having means for inspecting the mercury column and the contacts to be connected thereby. Other objects relate to various features of construction and arrangement which will appear more fully hereinafter.

T he nature of the invention will be understood trom the following speciication, taken with the accompanying drawings in which one embodiment is illustrated.

lu the drawings Fig. 1 shows a longitudinal section through the center line of the im proved switch, Fig. 2 shows a front elevation ot' the switch with the cover thereof re` moved, Fig. 3 shows an elevation of the rear side of the switch, Fig. 4 shows a sectional view on the line 44 of Fig. 1 and Fig. 5 shows a sectional view'on the. line. 5-5 of F ig. 2.

'lhe invention comprises a supporting base i0 ot' insulating material which is oblong in shape and provided with curved extremities. This insulating base is enclosed in a sheet metal casing 11 which is stamped to form an enclosure similar in shape to that ot the insulating base, being provided with an upper wall 11a and outer walls 11b. The upper wall has an oblong opening 12 formed therein and an annular tlange'13 extends upwardly around the edges of this'opening to receive the edges of the lateral walls 14a of a 4sheet metal cover 14, which closes the opening 12 and forms a chamber 15 on the outer side of the base 10. Two sheets of libre board or other insulating material 16 are mounted on the outer face of the base 10 and the ends of the base are provided with flanges 1()a of reduced thickness which are adapted to be engaged by the U-shaped metal clips 17. The inner arms of these clips are threaded to be engaged by screws 18 which pass through apertures in the'casing 11 and in the cover 14, thereby securing both of these parts and the clips in rigid position with respect to the supporting base.

The outer arm 20,01? the lower metal clip 17 is provided with a transverse, outwardly projecting iiange 21, which extends through openings 22 inthe insulating sheets 16, being provided with an opening 23 adapted to receive the bulb 24 of the mercury tube 25. The bulb 24 is frictionally engaged by a sheet metal gripping member .26 which is clamped around the bulb of the tube. and

provided with lateral flanges 27 adapted to engage notches 28 formed in the supporting flange 21 on opposite sides of the opening 23, as shown particularly in Fig. 5. The gripping member 26 is connected at 29 to a heat transmitting plate 80 which is provided with laterally extending arms 31 having a.

plurality of up-turned tongues 32 adapted to contact with the inner surface ot the cover 14, so that a direct connection is established between the metallic cover 14 and the metallic gripping member surrounding the bulb 24 of the mercury tube. This construction causes the mercury column to respond readily to changes in temperature in the air surrounding the metallic cover. rlhe arms of the supportingtlanges 21 are provided with tips 33 which are adapted to project between adjacent tongues. 32. thereby holding the transmitting member and the gripping member 26 against vertical displacement within the chamber 15.

The mercury tube 25 is provided at suitable points along its length with metallic contacts 35 and 36 which extend through the tube into the vertical opening therein to be engaged by the mercury column when it rises to suitable heights. Rings ot conducting material 37 are provided Varound the mercury tube at the points where'the contacts 35 and 36 are connected, and conductors 38 and 39 `lead from these contacts to the respective binding posts 4() and 41, which -and the cover 15.

extend through apertures in sheets 16 and are mounted on the insulating base in cavities 42 provided for that purpose. The conductors 43 and 44, leading to the external circuit, pass through an opening 45 formed in the boss 46 on the under side of the insulating base and these con,-` ductors are connected to the binding posts 40 and 41, respectively, as shown partlcularly in Fig. l.

In case the mercury tube becomes accidentally broken it is desirable that the electric circuit controlled thereby be closed so that the heating apparatus or other apparatus actuated b v the circuit will be opened, The terminal 40 is therefore provided with n a metal clip 47 and the terminal 41 is connected to a metal clip 48. The clip^48 eX- tends transversely beneath the mercury tube and is provided with a reversely bent resil1 ent arm 48a having a transverse pro'niection 481 adapted to rest on the outer surface of the mercury tube between the mercury tube The projection 48b engaging the mercury tube normally maintains the extremity 48c of the resilient arm out of engagement with the metallic clip 47 but if the mercury tube becomes broken the projection 48b is released and permits the arm 48ato move inwardly toward the base 10 until the extremity 48c engages the clip 47 and thereby establishes a connection between the terminals 40 and 41,. The metallic clip 48 and its resilient arm 48a are normally protected against accidental connection with the cover 18 by means of a curved sheet 50 of mica or other transparent insulating material which is mounted over the mercury tube with its edges inserted beneath the flanges 13 of the casing 11, as shown in Fig. 4. The inspection of the mercury contacts and the clips 47 and 48 through the transparent insulating sheet 50, is permitted by a glass window 51 which is secured in an opening 52 formed in the cover 15 by means of a metallic retaining member 58.

The metallic clip 17 at the upper end oi the insulating base has an outer arm 55, similar to the arm 2O of the iovver clip, and this arm is provided with a transverse flange 56 which extends outwardlythrough openings 57 formed in the insulating sheets 16. This Harige is recessed as shown at 58 to receive bushing 59, formed of rubber or other suitable material, which is engaged by the mercury tube 25. The bushing is' provided on its outer side with an annular groove 60 which engages the Walls of the recess 58 on its inner side, and is engaged on its outer side by a retaining member 61having the form illustrated particularly in Fig. 4. The extremities of the retaining member are proinsulat'ing v jected inwardly at 61a to be engaged by the reversely bent arms 62 which are formed on the supporting flange 55. The annular groove 60, formed in the bushing 59, has a greater Width vertically than the thickness of the liange 56 and the retaining member 61. A loose frictional engagement is provided between the bushing 59 and the contacting parts so that relative movement is permitted and the rictional engagement of the mercury tube with the bushing 59 may also be slightly loose in order to permit a limited relative movement of the tube with respect to the bushing. This limited movement of the mercurytube which is thus permitted is adapted to insure the stability of the mercury tube regardless of any blows or vibrations which may be imparted to the supporting base or its casing. The manipulation of the mercury column to establish a circuit between the contacts 35 and 36 is thus prevented. The loose support of the lower end of the mercury column is adapted to cooperate with the frictional chp on the upper end thereof to bring about the desired result. The means herein described for supporting the mercury tube are claimed in my co-pending application Serial No. 614,741, filed January 25, 1923.

Although one form oi the mercury tube switch has been shown and described for purposes of illustration, it will be understood that the invention may take various other forms without departing from the scope of the appended claims.

I claim:

1. A switch comprising a mercury tube, means for supporting said mercury tube adjacent each end thereof, a pair of contacts connected to said tube between said supports, a metallic clip connected to one of said contacts and provided with a resilient arm having a part engaging the outer side of said tube between said supports, and a second metallic clipv connected to the vother of said contacts and adapted to be engaged by said resilient arm upon breakage o? said tube between said supports.

2. A switch comprising a mercury tube rovided with a pair of tongue contacts to e connected by the mercury column, a pair of metallic contacts located outside of said tube and adapted to be connected upon breakage of said tube, a base for supporting said mercury tube, a metallic cover mounted over said tube and having a window therein opposite said contacts, and a sheet of transparent insulating material mounted within said cover over saidmetallic contacts.

Vl/'ILLIAM G. HARTWIG. 

